From 2x10 (Sram) to 3x10 (Shimano)

Given that my wife's 2010 stumpjumper came set up with a 3x9 slx derailleur, absolutely. Just make sure you use the correct mount. You need to match you front derailleur to the shifter so you will also need a 3x10 shifter. My question is why are you going from 2x10 to 3x10? If it is a gearing issue, it most likely can be solved by a chainring swap which will be less expensive and maintain the better shifting that a double front provides.